Epoxy resins, when used in combination with various curing agents, provide cured resins generally excellent in mechanical properties, water resistance, chemical resistance, and electrical properties and find their use in various fields such as adhesives, coatings, laminates, molding materials, casting materials, etc. In particular, their excellent characteristics and economical considerations have made them widely useful in semi-conductor sealing compounds.
Known epoxy resins include those produced by reacting epichlorohydrin with a novolak obtained by the reaction between 1,6-dihydroxynaphthalene and formaldehyde as disclosed in JP-A-2-227418, JP-A-61-69826, and JP-A-2-189326 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
However, since the reaction product between 1,6-dihydroxynaphthalene and formaldehyde is a mixture comprised of dimer, trimer, and other oligomers, the epoxy resin obtained by reacting such a mixture with an epihalohydrin is necessarily a mixture comprised of a dimeric epoxy resin, a trimeric epoxy resin, a tetrameric epoxy resin, a pentameric epoxy resin, etc. Such a mixed epoxy resin, though excellent in heat resistance, has a considerably high melt viscosity.